One additional note...
Last fall when I was winterizing the GL1800, I was using the POS spark plug socket from the GL1800 toolkit rather than digging in my tool chest for a better socket. Well, I ended up cracking the ceramic body of one of the plugs.
It was a Sunday afternoon, and not many parts stores open. The only place I could find that had the plugs carried the BRK6E not the BRK6E-11. A quick look on the NGK site shows that the "dash" number is the gap (-11 for 1.1 mm). If there is NO "dash" number, then the gap is .8mm. That is the only difference between the two.
So, I bought the BRK6E re-gapped them to 1.0-1.1mm and all is fine.
Just wanted to toss in another data point in case the parts store hands you plugs that are labeled as BRK6E with no "dash" number.